The present invention relates to a piezoelectric high voltage device, particularly concerning an improvement on the impact mechanism of the device in which the piezoelectric element is essentially struck by a straight-line directional force. This improvement has operational and economic advantages over prior art devices.
Piezoelectric high voltage devices of both impact type and gradual squeeze type are known in the prior art. The impact type devices have a considerable cost advantage over squeeze devices as less bulky arrangements are required in order to provide the necessary force, and dimensional tolerances are much less regid.
The impact type device of the prior art consists of housing means, which contains actuator means, ledge means contained within the housing means, actuator means contained within the housing means having a blind bore formed therein, an hammer means receivable in the housing means, an actuating spring means received within the blind bore and operably connected to the hammer means, and piezoelectric element means received in the housing which is responsive to mechanical actuation thereof to produce a spark.
The blind bore in the actuator means has a longitudinal axis offset from the longitudinal axis of the actuator means causing the actuating spring means and the hammer means to be positioned at an angle offset from the longitudinal axis of the housing means. This results in the engagement of the hammer means with the ledge means upon the inward movement of the actuator means in the housing means. During actuation of the mechanism, the actuating spring means is compressed as the hammer means is held on the ledge means by the offset position of the actuating spring means and is released as the actuator means forces the hammer means off the ledge means. The actuating spring then expands, throwing hammer against the piezoelectric element means to generate a high voltage pulse.
In the above-mentioned arrangement, the actuator means has slanted internal walls that hold the actuating spring means at an angle so that the hammer means is held by actuating spring means on internal ledge means before actuation.
Such an arrangement has a disadvantage that undesirable component or disperse forces may result and reduce the impact speed of the hammer against the piezeoelectric element means. Therefore, the high voltage pulse may vary from one impact to another impact. Also the piezoelectric element means is easily damaged under such unstable impact conditions, and frequent replacement of the device is costly.